A whine like a police siren could be normal or a sign of an unbalance rotating assembly. If it were a bad actuator, I would expect a hissing like an air leak, becuase that's what it would be.
You can check the actuator be removing it and applying pressure to one port (the one connected to the compressor's outlet) to make the rod come out. The other port should be connected to vacuum at the plenum, but I recommend disconnecting and capping it off (it doesn't do anything, but usually leaks).
Also, a boost gauge will tell you if the actuator is doing it's job or not.